Journal of University of Chinese Academy of Sciences

Iterated Hardy-Littlewood maximal function

WANG Zequn, YAN Dunyan

2018, 35 (4): 433-437. DOI: 10.7523/j.issn.2095-6134.2018.04.001

In the paper, we investigate the iterated non-centered Hardy-Littlewood maximal function and the iterated centered Hardy-Littlewood maximal function. We prove that the limit of the iterated maximal function is just a fixed point of maximal operator. As an application of the fixed point theory, we finally obtain that the fixed point is||f||_∞ for non-centered Hardy-Littlewood maximal operator. The same is true for the centered Hardy-Littlewood maximal operator only for n=1,2.

Construction of conformal minimal surfaces in HP³

ZHANG Wenjuan, CHEN Xiaodong

2018, 35 (4): 438-443. DOI: 10.7523/j.issn.2095-6134.2018.04.002

Abstract ( 263 ) PDF (KB) ( 0 )

In this paper, we construct ten families of conformal minimal surfaces immersed into HP³ by the twistor map π:CP⁷→HP³. The construction is based on Eells and Wood's conclusion in 1983 that the projection of a horizontal harmonic map is also harmonic. Firstly, we give a characterization theorem for horizontal holomorphic surfaces in CP⁷. By this theorem and Eells and Wood's conclusion, we get some conformal minimal surfaces immersed into HP³ by the twisted map.

Experimental study on suppression of liquid metal splashing in high magnetic field and electric field

LI Can, WANG Zenghui, JIA Xiao, NI Mingjiu

2018, 35 (4): 444-450. DOI: 10.7523/j.issn.2095-6134.2018.04.003

Abstract ( 348 ) PDF (KB) ( 0 )

The liquid metal, as the liquid first wall in the reactor, together with the high toroidal magnetic field, is propelled by electrodynamic force, which would cause the liquid metal free surface splashing and threaten the security and stability of the fusion reactor. In this paper, we use the capillary porous channel structure. It increases the contact area of the liquid metal with the wall, so that adhesion increases. It has an additional surface tension, which greatly reduces the wetting resistance and electromagnetic force, achieving the effect of suppression of splash. Liquid metal surface control can be improved by enhancement of surface wettability and the proper choice of liquid metal surface structure. The experiments are carried out in order to understand the causes and consequences of ejected liquid metal as well as to investigate the effects of surface structures on the ejection process.

Numerical simulation of the piston effect in superheated liquid R134a

HUANG Caifeng, LI Yuhua, LI Zhigang, GUO Chaohong, JIANG Yuyan

2018, 35 (4): 451-456. DOI: 10.7523/j.issn.2095-6134.2018.04.004

Abstract ( 412 ) PDF (KB) ( 0 )

In this paper, a model of one-dimensional cavity filled with meta-stable superheated liquid R134a is built to investigate influence of the piston effect (PE). Numerical simulation method is used in boundary condition of a temperature jump. The PE is caught in the superheated liquid by solving energy transport equation of compressible fluid. Then the equivalent thermal conductivity of PE is calculated. Furthermore, the influence of liquid superheat degree on piston effect is investigated. The higher the superheat degree is, the stronger the PE effect is. In conclusion, the piston effect is capable of carrying higher heat flux and speeding up thermal equilibrium in superheated liquid of R134a. The equivalent thermal conductivity of PE is obviously superior to pure heat conduction, and the equivalent thermal conductivity of PE is tripled.

Role of the Skyrme tensor force in heavy-ion collision

YU Chong, GUO Lu

2018, 35 (4): 457-462. DOI: 10.7523/j.issn.2095-6134.2018.04.005

Abstract ( 327 ) PDF (KB) ( 0 )

In this paper, we studied the role of Skyrme tensor force in ¹⁶O +⁴⁰Ca collision using the time-dependent Hartree-Fock (TDHF) theory with the full terms of Skyrme effective interaction. The calculations were carried out in three-dimensional Cartesian bases without any symmetry restrictions. The TDHF theory incorporates various quantum effects including Pauli effect and spin-orbit coupling. We systematically studied effects of the Skyrme tensor force on Coulomb barrier, upper fusion threshold energy, and Skyrme energy density functional for the¹⁶O +⁴⁰Ca system. The Skyrme tensor force has no influence on Coulomb barrier in the spin-saturated system ¹⁶O +⁴⁰Ca, and the tensor force plays a non-negligible role for upper fusion threshold energy. The isoscalar and isovector tensor terms and the rearrangement of mean-field tend to increase the upper fusion threshold energy. The tensor force leads to some changes in Skyrme energy density functional. The isoscalar tensor term and the rearrangement of mean-field increase the total energy contributions of pseudotensor spin-current term, while the isovector tensor term and the rearrangement of mean-field decrease the total energy contributions of pseudotensor spin-current term.

Average elastic thickness of the Moon estimated using admittance

YANG Yongzhang, LI Jinling, MATSUMOTO Koji, HANADA Hideo, LI Wenxiao

2018, 35 (4): 463-467. DOI: 10.7523/j.issn.2095-6134.2018.04.006

Abstract ( 398 ) PDF (KB) ( 0 )

In this paper, we consider the free-air gravity model by the GRAIL (Gravity Recovery and Interior Laboratory) mission and the topographic model from the LRO (Lunar Reconnaissance Orbiter) laser altimetry. They showed high correlation up to~500 (0.8) degree. The gravity-topography admittance (the ratio of gravity to topography in spectral domain) was low for degrees below~50 (i.e., wavelength longer than~220 km), but it increased sharply and was kept at constant value of~110 mgal/km. We employed the Gauss-Newton method and simple model to estimate the elastic thickness of the Moon at 11.76 km. This thickness value is not significantly different from those found in the present Earth in spite of the smaller dimension of the Moon. This implies that the significant portion of topographic features on the Moon was formed in the early ages of the Moon, when the heat flow was comparable to that in the present Earth.

Photometric metallicity of the galactic halo based on SCUSS and SDSS

ZUO Wenbo, DU Cuihua

2018, 35 (4): 468-472. DOI: 10.7523/j.issn.2095-6134.2018.04.007

Abstract ( 268 ) PDF (KB) ( 0 )

Based on the correlation between[Fe/H] of F-/G-type main-sequence star and color index, we simulate the distribution of metallicity of the halo star using Monte-Carlo method based on u-g and g-r from SCUSS and SDSS. We select F-/G-type main-sequence star in halo as tracer and study the sample in the Z<-10 kpc,Z<-12 kpc, and Z<-15 kpc intervals, where Z represents the distance of the star from the galactic plane. The metallicity distribution of selected stars in every interval can be fitted by three-Gaussian model, with peaks at[Fe/H]~-0.60,-1.55, and -2.20. Based on our analysis, we find that the two components with metal-poor peaks are associated with the inner and outer halo and the metal-rich component is contributed by substructure in the halo.

Reactive oxygen species accumulation induced by D-amino acid in Saccharomyces cerevisiae

LIU Qingju, HE Yujian, WU Li, LI Xiangjun

2018, 35 (4): 473-480. DOI: 10.7523/j.issn.2095-6134.2018.04.008

Abstract ( 335 ) PDF (KB) ( 0 )

D-amino acids occur widely in food. Reactive oxygen species accumulation and biochemical damage caused by D-amino acids to Saccharomyces cerevisiae are evaluated. The results show that cell growth is inhibited and level of H₂O₂ increases after exposure to D-amino acids, which leads to high levels of catalase and peroxidase activities. All these facts suggest that hydrogen peroxide is the main ROS induced by D-amino acids and oxidative damage is the primary mechanism by which D-amino acids exert toxic effect on Saccharomyces cerevisiae cells.

Performance of doxorubicin-loaded hyperbranched polyglycerol nanoparticles

FA Mengmei, LIU Xu, WANG Ailian, ZHANG Liaoyun, YAO Xin

2018, 35 (4): 481-486. DOI: 10.7523/j.issn.2095-6134.2018.04.009

Abstract ( 362 ) PDF (KB) ( 0 )

Hyperbranched polyglycerol (HPG) with the molecular weight of 5 000 was synthesized from the glycide monomer via anionic polymerization. HPG nanoparticles loaded with different amounts of doxorubicin (DOX) were evaluated by fluorescence and scanning electron microscope. The results showed that HPG had good loading ability for DOX. The drug loading capacity reaches 7.25%. The doxorubicin-loaded HPG nanoparticle also showed slow-releasing and target-releasing behavior. The sustained release was kept on over 20 h. All these properties of HPG nanoparticle suggest its promising potential as an effective controlled anticancer drug-delivery system.

Molecular dynamics simulation of self-assembly process of DNA and B-PDEAEA

HUANG Xuqi, LI Xiaoyi

2018, 35 (4): 487-491. DOI: 10.7523/j.issn.2095-6134.2018.04.010

Abstract ( 405 ) PDF (KB) ( 0 )

The self-assemble processes of DNA/B-PDEAEA nanoparticles are investigated by means of molecular dynamics simulations. The simulation results show that the electrostatic interaction force is the main driving force for the self-assembly process. At the same N/P ratio,stable nanoparticles form easier when the number of DNA base pairs is larger. With the same number of base pairs, stable nanoparticles form easier at larger N/P ratio.

Forming mechanism of mica iron oxide from glazed tiles in Yuanmingyuan

DOU Jinhai, WANG Caiqi, CUI Jianfeng, JIN Hetian, ZHANG Zhonghua

2018, 35 (4): 492-499. DOI: 10.7523/j.issn.2095-6134.2018.04.011

Abstract ( 293 ) PDF (KB) ( 0 )

This experiment analyzes the diffused red in yellowing phenomenon of partial yellow glazed tiles unearthed from Yuanmingyuan by means of optical microscope, EDXRF, SEM, XPS, and XRD in order to study the color change mechanism. The analyses suggest that the glaze layer of the sample tiles belongs to a kind of lead silicate glass and that the diffused red in yellowing phenomenon of glaze is due to the different forms of Fe within the glaze layer, with α-Fe₂O₃ crystal dominating the red area and Fe³⁺ and Fe²⁺ existing simultaneously in the yellow area. The study shows the phenomenon can be explained by the process of oxidation of Fe²⁺ into Fe³⁺in the yellow area at high temperature during which glaze layers are lost. It further results in abundant precipitation of Fe³⁺ in the form of hexagonal plate α-Fe₂O₃ crystal particle, which is also called micaceous iron oxide red being very important rust preventive and pearlescent pigment.

Spatial pattern of correlation of summer precipitation in Qinghai-Tibetan Plateau with East Asian and South Asian summer monsoon indices

GAO Dong, NIU Haishan

2018, 35 (4): 500-505. DOI: 10.7523/j.issn.2095-6134.2018.04.012

Abstract ( 294 ) PDF (KB) ( 0 )

Influence of East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM) on summer precipitation in Qinghai-Tibetan Plateau was evaluated, based on dataset CRU_TS4.0, East Asian summer monsoon index (EASMI), and South Asian summer monsoon index (SASMI). By using partial correlation method, the tempo-spatial pattern of summer precipitation in the region was also examined. The results showed that SASM was associated with much larger area than EASM.SASM was positively correlated with precipitation in part of the southern plateau,while was negatively correlated with the middle, the north, and the west of the plateau. Positive correlation between EASM and precipitation was found in Qaidam Basin and surrounding regions.

Spatial-temporal distribution characteristics and simulation of population in the main urban area of Urumqi City from 1982 to 2010

YANG Zhen, LEI Jun

2018, 35 (4): 506-514. DOI: 10.7523/j.issn.2095-6134.2018.04.013

Abstract ( 335 ) PDF (KB) ( 18 )

Spatial distribution of population in the main urban area of Urumqi City was studied from the perspectives of concentration index,population agglomeration index, population density changs in different spheres, monocentric and polycentric population density simulations, and space reconstruction. This work reveals the characteristics and laws of the population growth and distribution in the main urban area of Urumqi City. The main conclusions are given as follows. 1)The concentration degree of population distribution could be divided into two stages, the rapid growth stage from 1982 to 2000 and the slow growth stage from 2000 to 2010. From the viewpoint of the population agglomeration index, the agglomeration characteristics of population distribution were obvious, and the agglomeration presented a band feature along the main traffic corridor. 2) The population density maintained a centralized regular pattern. 3) Based on the regression of monocentric model, population density models of the main city area were different for the four years. The inverse function model was better for 1982 and 2000 while the cubic function model was fit for 1990 and 2010. Based on the regression of polycentric model, the authors found that a double-center structure appeared in the main city area in 2010. The main center played an important role in affecting the population distribution, and the subcenter was weak in the agglomeration population capacity.

Intracavity frequency-doubled passively mode-locked Nd: LuVO₄ green laser

LI Bei, YU Haijuan, HE Chaojian, QI Yaoyao, CHEN Han, LIN Xuechun

2018, 35 (4): 515-520. DOI: 10.7523/j.issn.2095-6134.2018.04.014

Abstract ( 314 ) PDF (KB) ( 1 )

We demonstrated an intracavity frequency-doubled passively mode-locked Nd:LuVO₄-LBO green laser with SESAM as the saturable absorber. The maximum average output power was 385 mW when the pump power was 9.3 W. The pulse width was 17.6 ps and the repetition rate was 76 MHz. The optical conversion efficiency from the pumping diode laser to the green laser was 4.1%. We observed the interference of the frequency-doubled green light with the normal operation of SESAM, analyzed the reason, and eventually resolved the problem.

A format feature extracting and classifying algorithm for unknown data link frame

XUE Kaiping, LIU Bin, LI Wei, HONG Peilin

2018, 35 (4): 521-528. DOI: 10.7523/j.issn.2095-6134.2018.04.015

Abstract ( 259 ) PDF (KB) ( 0 )

With the rapid development of communication network, private protocol is widely adopted. Without necessary prior knowledge, the existing analyzing tools for the open protocols cannot be used for obtaining the information from the private protocol data. To get the information from the private protocol data, one has to extract the protocol format feature and classify the protocol data correctly. Based on the general rules of protocol format, a format feature reverse extracting and data classifying algorithm was proposed for unknown data link frame. By data link frame precoding and fixed-field mining, the frame format features can be extracted from the frame sample set and the feature vectors can be calculated. Finally, the data link frames are classified based on the weighted Euclidean distances between the feature vectors. The test results show that the proposed method can be used to extract the protocol format features effectively and to correctly classify the data link frames by using format features.

Multi-path clutter suppression in passive radar reference channel based on digital TV signal

ZHAO Xufeng, LI Daojing, HU Xuan

2018, 35 (4): 529-535. DOI: 10.7523/j.issn.2095-6134.2018.04.016

Abstract ( 315 ) PDF (KB) ( 0 )

Passive radar, which uses a third-party radiation source signal for moving target detection, plays a vital role in present and future electronic warfare. It usually uses the correlation detection method, but the reference signal is often accompanied by multi-path clutter interference. Simulation results show that multi-path clutter in the reference signal reduces the performance of target detection, increases the false alarm, and lifts the detection base. So suppressing multipath clutter is the main problem. In this paper, the principle of suppressing multipath clutter using k-forward prediction algorithm is given, and the filtering is realized based on least mean square error criterion. The simulation and real-life data results confirm the effectiveness of the proposed algorithm.

Imbalanced fuzzy multiclass support vector machine algorithm based on class-overlap degree undersampling

WU Yuanyuan, SHEN Liyong

2018, 35 (4): 536-543. DOI: 10.7523/j.issn.2095-6134.2018.04.017

Abstract ( 348 ) PDF (KB) ( 13 )

Undersampling is a commonly-used method for data reconstruction. This method is used to solve the problem of imbalanced data classification. However, the traditional undersampling method often loses important sample information, and lacks stabilities of experimental results. To settle these two problems, this paper proposes an imbalanced fuzzy multiclass support vector machine algorithm based on class-overlap degree undersampling. This algorithm combines LOF local outlier factor and box-whisker plot to delete noise samples in the training datasets, then extracts support vectors based on class-overlap degree. Finally, the class-overlap degree of each sample is set as the membership value of this sample, and the fuzzy multiclass support vector machine is constructed. Experimental results show that our algorithm overcomes the disadvantages that the support vector machine with random undersampling often loses the important sample information and the unstabilities of experimental results. In addition, our algorithm improves the classification accuracy of support vector machine in imbalanced and noisy datasets.

Spatio-temporal-fused no-reference video quality assessment based on convolutional neural network

WANG Chunfeng, SU Li, HUANG Qingming

2018, 35 (4): 544-549. DOI: 10.7523/j.issn.2095-6134.2018.04.018

Abstract ( 335 ) PDF (KB) ( 0 )

No-reference video quality assessment (NR-VQA) measures distorted videos quantitatively without the reference of original distorted-less videos. Most conventional NR-VQA methods are based on statistical analysis, and the majority of them are generally designed for specific types of distortions or consider less about the temporal information, which limits their application scenarios as well as their speeds. In this paper, we propose a spatio-temporal no-reference video quality assessment method based on convolutional neural network, which is not designed for specific types of distortions. We divide the method into spatial and temporal processes. We redesign a convolutional neural network in spatiality to learn the distortion features in frames. A group of SSIM-like features are exploited in temporality. Finally, we train a linear regression model using the spatio-temporal features to predict the video quality. Experiments demonstrate that the proposed method is similar to other state-of-the-art no-reference VQA methods in performance. Fourthermore, the proposed method runs much faster than other VQA methods, which makes the proposed method have better application prospects.

Microblog users' Big-Five personality prediction based on multi-task learning

ZHENG Jinghua, GUO Shize, GAO Liang, ZHAO Nan

2018, 35 (4): 550-560. DOI: 10.7523/j.issn.2095-6134.2018.04.019

Abstract ( 642 ) PDF (KB) ( 10 )

Most of traditional prediction methods of social network users' personality are based on single-task classification or regression machine learning. They ignore the potential related information between multiple tasks, and are very difficult to get admirable prediction results based on small scale training data. In this paper, a robust multi-task learning method (RMTL) is proposed to predict Big-Five personality of Microblog users, and it can not only share the task relations, but also identify irrelevant (outlier) tasks. The model is first decomposed into two components, i.e., a structure and an outlier, and then the nucleus norm and L₁/L₂ norm are used to constrain the regular term so as to solve the optimization problems. With Sina Microblog users' data, we validate the RMTL method, and the average correct rate, average precision rate, and average recall rate of the five dimensions are 67.3%, 71.5%, and 74.6%, respectively. The RMTL method outperforms the 4 single-task learning methods and the multi-task learning.

Compression deformation test and rupture mode study of the marine shales from Wufeng-Longmaxi Formations in the southern margin of Sichuan Basin

XU Tianyang, JU Yiwen, HUANG Cheng, QI Yu, ZHU Hongjian

2018, 35 (4): 561-568. DOI: 10.7523/j.issn.2095-6134.2018.04.020

Abstract ( 266 ) PDF (KB) ( 0 )

The key to shale gas exploration and exploitation is to form a large-scale fracture network through fracturing technology. The technology is based on the friability evaluation of shale reservoirs, which is closely related to the rock mechanics and deformation characteristics. Based on the observation of the macro and micro characteristics of the marine shales from Wufeng-Longmaxi Formations in the southern margin of Sichuan Basin, we obtained its rock mechanical parameters through uniaxial compression deformation tests. By combining the stress-strain curves and analysis of rupture morphology, we obtain the results as follows. The shale shows relatively low compressive strength and Young's modulus, and has significant brittle characteristics. The shale has two rupture modes, single cant shear rupture and splitting rupture, which are decided by the bedding and loading directions. The mechanical properties and rupture modes of shale are influenced by many factors, among which the heterogeneity is the most important.

CCI: a containerization-based continuous integration system

ZHANG Zhaochen, LUO Tiejian

2018, 35 (4): 569-575. DOI: 10.7523/j.issn.2095-6134.2018.04.021

Abstract ( 306 ) PDF (KB) ( 0 )

With the increasing of software complexity and the changing of project requirements, it is the main consideration in software development to realize the rapid application delivery with high quality. However, traditional software-build methods lack team cooperation and standardized process management, and one needs to invest a lot of time and cost to ensure software quality. In order to solve this problem, we build a continuous integration system based on Jenkins and standardize the software environment by using Docker technology. The experimental results show that Docker reduces the complexity of building environment by more than 90%, improves the portability and diversity of the testing environment, and greatly increases the efficiency of software development.

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